In order to meet the demand of high-density and high-transmission rate, reduction in component size, and high production scalability, the deployment of Planar Lightwave Circuits (PLC) and related waveguide packaging is undoubtedly the trend in the optical networking industry. An optical fiber array is used for the connection of light input/output ends of optical fibers to a waveguide substrate. Since the alignment accuracy for such a connection requires tolerances at the submicron level, the method of fabrication of the optical fiber array is crucial to achieve and maintain high-product yields of PLC devices. Moreover, to increase the density and reduce the size of the waveguide, efforts are being made to reduce the waveguide pitch and thus the inter-fiber pitch of a fiber array down to 127 μm, which is approximately half of the standard waveguide pitch of 250 μm.
In order to obtain an accurate pitch in an optical fiber array, a v-groove substrate commonly are made by using: (1) wet etching of a Si substrate; (2) slicing of a glass substrate; or (3) molding of a plastic substrate. However, the operation of arranging the bare optical fibers and setting them into the predetermined v-grooves is a very difficult task. For example, FIGS. 1(a)-(b) show the setting of bare fibers 33 into the predetermined v-grooves of substrate 30 for a half-pitch optical array. FIG. 1(a) shows ribbon fibers 31 and 32. Each include four optical fibers 33 surrounded by a coating 34. After removing the coating 34, bare fibers 33′ are exposed. However, it is difficult to keep the same inter-fiber pitch without the coating as the fibers tend to separate and spread out. As shown in FIG. 1(b), as the bare fibers 33′ are pressed against the substrate 30, the bare fibers 33″ do not align with the v-grooves. In other words, some of the bare fibers 33″ are positioned outside the v-grooves. In order to guide these loose, bare fibers after removal of the coating, the conventional method is to adopt a positioning guide fixture to arrange the bare fibers so that the inter-fiber pitch is approximately the same as the v-groove pitch of the substrate 30. Unfortunately, however, the positioning guide fixture can require very accurate and sophisticated machinery, which adds extra cost to the manufacturing costs associated with an optical fiber array product.